docs: def _get_proj_convex_hull(self):
          """
          Create a projection centered in the center of this mesh and define
          a convex polygon in that projection, enveloping all the points
          of the mesh.
  
          :returns:
              Tuple of two items: projection function and shapely 2d polygon.
              Note that the result geometry can be line or point depending
              on number of points in the mesh and their arrangement.
          """
          # create a projection centered in the center of points collection
          proj = geo_utils.OrthographicProjection(
              *geo_utils.get_spherical_bounding_box(self.lons, self.lats))
  
          # project all the points and create a shapely multipoint object.
          # need to copy an array because otherwise shapely misinterprets it
          coords = numpy.transpose(proj(self.lons.flat, self.lats.flat)).copy()
          multipoint = shapely.geometry.MultiPoint(coords)
          # create a 2d polygon from a convex hull around that multipoint
          return proj, multipoint.convex_hull